Polysomnographic features of REM sleep behavior disorder: development of a scoring method.

REM sleep behavior disorder (RBD) is characterized by the intermittent absence of REM sleep EMG atonia and the appearance of elaborate motor activity associated with dream mentation. There are no specific diagnostic criteria for RBD based upon polysomnographic findings. We describe a new scoring method and show its sensitivity to treatment with clonazepam. An increased phasic submental EMG density occurs in RBD patients, but REM density is similar to that of controls. Clonazepam selectively decreases REM sleep phasic activity but exerts no effect on REM sleep atonia. Periodic limb movements in sleep (PLMS) occur equally in both REM and NREM sleep in RBD patients, suggesting that normal suppression of PLMS in REM sleep is due to motor inhibition.